Alkylation of hydrocarbons



Patented Dec. 3,1940

UNITED STATES PATENT OFFICE 2,223,938 snxmrrou or HYDROCARBONSApplication May 6, 1939, Serial No. 272,160

6 Claims.

This invention relates to-the alkylation of hydrocarbons in the presenceof a catalyst. It is.

' 15 tively low-boiling point oleflns, such as oleflns 7 containing fromthree to four carbon atoms to produce alkylation products within thegasoline boiling range and having a high anti-knock value.

The invention broadly contemplates a continuous method of alkylationwherein paraflin and olefin hydrocarbons are passed through an extendedzone of reaction or through a zone of reaction comprising a plurality ofreaction stages. The hydrocarbons are passed concurrently with usedcatalyst through the initial portion of the reaction zone, while freshcatalyst is introduced to the reaction zone at an intermediate point orstage. Used catalyst may be withdrawn from an intermediate point orstage, or from a point or stage substantially beyond that at which thefresh catalyst is introduced and recycled to the initial portion of thereaction zone for contact with the hydrocarbon feed.

The catalyst advantageously comprises strong sulphuric acid having aconcentration of about 88 to 100% H2804, and preferably about 94%.

However, it is contemplated that otherliquid alkylation catalystseffective for the purp se may be employed as, for example, the catalystpre 30 pared by introducing BF: into water until complete'saturation isobtained.

Pending application Serial No. 148,978, flied by Carl Korpi and ArthurR. Goldsby' June 18, 1937, describes alkylation of paraflinhydrocarbons, such as isobutane, with oleflns in, the presence of aliquid catalyst of the sulphuric acid type.

The present invention has to do withmodifications 'in the method ofcarrying out the alkylation process therein described. A

In. the continuous operation of the process is desirable to reuse thecatalyst, for example, by recycling the used acid in the system. Somedeterioration of the catalyst occurs during the process and this appearsmost noticeable in those portions or stages of the reaction zone towhich the fresh olefin hydrocarbon is introduced.- It is desirable,however, to prevent substantial deterioraticn since it reduces theefllciency oi' the process; I

In accordance with the present invention the olefin hydrocarbons arefirst brought into contact with used catalyst while fresh makeupcatalyst is introduced to the reaction zone at a point substantiallybeyond that at which the olefln hydrocarbon is introduced. The usedcatalyst to which the olefln hydrocarbon is initially sub- Jected tocontact is advantageously a portion of the liquid catalyst drawn offfroman intermediate-stage or from a stage substantially beyond that atwhich the fresh catalyst is introduced.

In order to disclose the invention more fully reference will now be madeto the accompanying drawing showing methods of flow adapted to thepractice of the invention.

In Fig. 1 the hydrocarbon feed containing 10 paraflin and oleflnhydrocarbons is conducted from a source not shown through a pipe I,which may communicate with one or more mixers 2,

3 and 4, as indicated. Used or recycle catalyst, such as sulphuric acid,from a subsequent stage is introduced to the mixer 2 from a pipe 5. Therecycle acid may also be introduced, if desired,

to either or both of the mixers 3 and l The hydrocarbon feed and recycleacid is subjected to complete agitation and mixing in the g0 mixer ormixers.

From the mixer 2 the mixture overflows to the mixer 3, wherein it issubjected to further mixing. From mixer 3 it overflows to the mixer 4.

Obviously the arrangement and number of mixers may be varied, asdesired, in order tosubject the hydrocarbons to contact with thecatalyst'for the desired length of time.

The overflow from the mixer 4 passes to asettler 8 whereinsettlingoccurs. The spent acid settles to the bottom ofthe vessel, fromwhich it may be drawn oil through a pipe I.

The hydrocarbon 'mixture collecting in the upper portion of 'the settler8 is drawn of! and passed to a mixer I wherein it is brought intocontact with freshly introduced acid of proper concentration.

After complete mixing the liquid is drawn of! to the mixer 9, wherein itis subjected to additional time of contact in order to complete the 40reaction. The reaction products from the mixer 8 are then drawn oif toasettler I0. The used acid settles to the bottom of the settler I0 andfrom there is drawn off through the pipe 5,.previously referred to, andby which means it is returned, all or in part. to the initial reactionzone.

The hydrocarbon reaction products accumulating in the settler ID areconducted to a neutralizer ll wherein they are treated with alkali.

The neutralized products are then conducted to a stabilizer l2 andtherein subjected to fractionation. Unreacted isoparamn, such asisobutane, is removed as a distillate through condenser It and collectedin receiver II. From receiver i5 fractionator I2 is drawn of! throughpipe It to a fractionator II. :From the top of fractionator I! agasoline fraction of about 311 F. end point is removed and condensed ina condenser l3. The higher boiling liquid constituents are withdrawnfrom the bottom of the fractionator.

Referring to Fig. 2, the hydrocarbon feed containing parafiin and olefinhydrocarbons is introduced to a mixer 20 'wherein it is subjected tointimate contact with used acid drawn off from a subsequent stage, aswill be described later. The mixer overflows to a settler2l. Thehydrocarbon layer at the top of the settler 2i overflows to a mixer 22,wherein it is brought into intimate contact with fresh concentratedacid.

The mixture from mixer 22 flows to a settler 23 where separation into ahydrocarbon and an acid layer occurs.

The hydrocarbon layer is conducted to a mixer 24 and therein broughtinto contact with used acid drawn off from the bottom of the settler 2i.

This mixture-then flows in succession through one or more mixers, suchas 25 and 26. From the mixer 26 it passes to a settler 21. Thehydrocarbon layer separated in the settler 2? is drawn ofi from the topthereof as the reaction products or alkylate and may be neutralized andfractionated, as previously described in connection with Fig. 1.

The acid layer formed. in the bottom of the 40 settler 21 constitutesthe spent acid which may be withdrawn from the system.

The acid' layer formed in the bottom of the settler 23 is drawn off, asindicated, and recycled to the mixer 20, and thus provides strong acidwith which the hydrocarbon feed is initially treated. v

In Fig. 3 the hydrocarbon feed is introduced to a mixer 30, wherein itis brought into contact with used acid from a subsequent stage. This 50mixture flows to a settler 3l and the hydrocarbon layer from thesettler-3| flows to a mixer 32. Fresh acid is introduced to the mixer 32and the resulting mixture of hydrocarbon and acid flows 55 to a settler33. The hydrocarbon mixture from the top of the settler 33 passes to amixer 34 and from there to a settler 35.

The hydrocarbon layer from settler 35 flows a mixer 36 and from there toa settler 3T.

The acid layer formed in the bottom of the settler 33 is drawn offand'recycled to the mixer 30, while the acid layer from the settler ,3! isdrawn off and conducted to the mixer 36.

The acid layer from the final settler 31 is re- 65 cycled to the mixer34. The alkylate drawn ofi from the settler 31 likewise is subjected toneutralization and fractionation, as described in' Fig. 1.

Comparing the methods of flow illustrated in the three figures, it winbe observed that Fig. 1

shows a. countercurrent system in which the acid is introduced to themixer 8 and flows concurrently with the hydrocarbon charge throughmixers 8 and 9. The acid separated in the settler 75 I then passes tothe mixer 2 and flows concurrently with the fresh hydrocarbon chargethrough mixers 2, 3 and 4 in series.

Fig. 2 shows a. combination of concurrent and countercurrent flow inwhich stages I and 2 (stage I comprising vessels 2!! and 2| and stage 2vessels 22 and 23) involve countercurrent flow. while the remainingstages involve concurrent flOW. T

Fig. 3 shows a countercurrent system in which the acid is introduced tothe mixer 32 and passes from settler 33 to the mixer 30, where it ismixed with the fresh hydrocarbon charge. The acid then passes from thesettler 3| to the mixer 36 and thence flows countercurrently to thehydrocarboncharge through the last two stages.

It is, of course, contemplated that any number of stages may beemployed, either'less than or more than those illustrated above.Furthermore, it is contemplated that instead of using a series ofindividual stages a single long reaction zone of the column or towertype may be employed, with provision for introducing liquid to .andwithdrawing liquid from a multiple of points "throughout its length.

The paramn hydrocarbons charged to the process should contain-asubstantial amount. of-

isoparafiins and may be any mixture of hydrocarbons containingisoparafiins which may be alkylated with olefins in the presence of acatalyst. Adesirable parafiln feed is one containing low-boilingisoparaflins, preferably isobutane or a mixture containing a largeproportion of isobutane. For example, products from the debutanizationor fractionation of straight run gasoline, or the product from thestabilization of natural gasoline, containing substantial proportions ofisobutane, may be used.

The olefin charge may comprise normally gaseous olefins, normally liquidolefins, or a mixture of both. Olefin containing gas such as producedfrom cracking plants, and sometimes referred to" as drum gas" can beused. Also gaseous products from dehydrogenation may be employed. A C4fraction or mixed C3 and C4 fraction from plant cracking gas,constitutes a very satisfactory olefi'nic charge stock.

The operation is conducted under sufiicient pressure to maintainthe'hydrocarbons undergoing treatment in a liquid condition. Where agaseous olefin is employed it may be injected in the recycling stream ofused acid.

It is desirable to maintain in the alkylation reaction zone isoparaflinsubstantially in excess of that required for reaction with the olefins.The ratio of isoparafiin to olefins may be between about 311 and :1 orover. Lower ratios may be employed but preferably in excess of 1:1.

As already indicated, the sulphuric acid catalyst has a concentration ofabout 90 to 100% H2804. The addition of new acid to an intermediatepoint in the system, as previously described, serves to fortify the acidand maintain the desired concentration throughout the reaction zone.

The amount ofnew acid added may be between about one-quarter to fivetimes the volume of oleflns. The temperature of reaction maintained ineach stage may range from about 30? to 125 F. and preferably about 60 to90 F.

Obviously'many modifications and variations of the invention, ash'ereinbefore set forth, may

' be made without departing from the spirit and We claim: I

1. In a continuous process for the alkylation of hydrocarbons in whichisoparaflin and olefin hydrocarbons are reacted in the presence of aliquid alkylation catalyst'during flow through a series of reactionstages, the steps comprising passing the hydrocarbons to an-initialstage in the series, subjecting the hydrocarbons to contact therein witha partially spent catalyst withdrawn from a succeeding and intermediatestage, withdrawing ,used catalyst from said initial stage, passing theinitially treated hydrocarbons to said succeeding stage, introducingfresh catalyst to said succeeding stage, subjecting the initiallytreated hydrocarbons to intimate contact with the fresh catalyst,withdrawing spent catalyst from said succeeding stage for use in theinitial stage, passing the, treated hydrocarbons from said succeeding.

, series.

spent catalyst withdrawn from asucceeding and intermediate stage,withdrawing used catalyst from said initial stage, passing the initiallytreat ed hydrocarbons to said intermediate stage, introducing freshcatalyst to said intermediate stage, subjecting the hydrocarbons tointimate contact with the fresh catalyst in the intermediate stage,withdrawing partially spent catalyst from said intermediate stage foruse in the initial stage, passing the treated hydrocarbons from saidintermediate stage to a final stage, introducing used catalyst withdrawnfrom the initial stage to said final stage, subjecting the hydrocarbonsin the final stage to contact with the used catalyst so introduced, andseparately discharging the hydrocarbon product and spent catalyst fromsaid final stage. i

4. The method according to claim 3 in which the liquid catalystcomprises sulphuric acid having a concentration of about to H2804.

5. In a continuous process for the alkylation of hydrocarbons in whichisoparaflin and olefin hydrocarbons are reacted in the presence of aliquid alkylation catalyst duringflow through a plurality of stages inseries, the steps comprising passing the hydrocarbonsto the first stagein the series, subjecting them to contact therein with partially spentcatalyst withdrawn from the second stage withdrawing used catalyst fromthe first stage, passing the initially treated hydro carbons tosaidsecond stage,- introducing fresh catalyst to the second stage,subjecting the hydrocarbons to intimate contact with the fresh catalystin the second stage, withdrawing partially spent catalyst from saidsecond stage for return to the first stage, passing the hydrocarbonsfrom the second stage to the third stage, subjecting them to contacttherein with partially spent .catalyst withdrawn from the fourth andfinal stage of the series, discharging spent catalyst from said thirdstage, passing the hydrocarbons from the third to the fourth stage,subjecting the hydrocarbons in the fourth stage to contact with usedcatalyst withdrawn from the first stage and discharging the hydrocarbonprod-. not from said fourth stage.

6. The method according to claim 5 in whichthe liquid catalyst comprisessulphuric acidhaving a concentration of about 90 to 100% H2804.

ERNEST F. PEVERE. LOUIS A. CLARKE. GEORGE B. HATCH.,

